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The GAMMAINV formula returns the inverse of the gamma cumulative distribution function for a given probability. This function is most commonly used for statistical analysis, particularly in modeling and simulation applications.


Use the GAMMAINV formula with the syntax shown below, it has 3 required parameters:

=GAMMAINV(probability, alpha, beta)
  1. probability (required):
    The probability at which to evaluate the inverse gamma cumulative distribution function. Must be between 0 and 1.
  2. alpha (required):
    The shape parameter of the gamma distribution. Must be greater than 0.
  3. beta (required):
    The scale parameter of the gamma distribution. Must be greater than 0.


Here are a few example use cases that explain how to use the GAMMAINV formula in Google Sheets.

Estimating wait times

Suppose we are modeling the wait time for customers at a restaurant and we know that the wait time follows a gamma distribution. We can use GAMMAINV to calculate the maximum wait time that we expect to see with a certain probability, based on our estimated shape and scale parameters.

Analyzing failure rates

In reliability engineering, the gamma distribution is often used to model the failure rate of a system over time. GAMMAINV can be used to estimate the time at which a certain proportion of the system is expected to fail, given the estimated shape and scale parameters.

Modeling insurance claims

The gamma distribution is commonly used in actuarial science to model the frequency and severity of insurance claims. GAMMAINV can be used to estimate the amount of insurance claims that are expected to exceed a certain threshold, given the estimated shape and scale parameters.

Common Mistakes

GAMMAINV not working? Here are some common mistakes people make when using the GAMMAINV Google Sheets Formula:

Using incorrect probability value

One common mistake is to use a probability value outside the range of 0 to 1. Make sure to use a valid probability value.

Switching alpha and beta values

Another common mistake is to switch the order of the alpha and beta values in the formula. Make sure to use the correct order.

Not using numerical values for inputs

The GAMMAINV formula requires numerical values for the probability, alpha, and beta inputs. Make sure to use valid numerical values.

The following functions are similar to GAMMAINV or are often used with it in a formula:


    The GAMMA function returns the Gamma function evaluated at the input value. The Gamma function is a commonly used function in mathematics, and is used in many statistical calculations. It is defined as the integral of t^(x-1)*e^(-t) from 0 to infinity. The GAMMA function can be used to calculate probabilities of certain events in statistical distributions.


    The GAMMALN function returns the natural logarithm of the absolute value of the Gamma function, Γ(x). The Gamma function is defined as an extension of the factorial function to complex and real numbers. The function is commonly used in probability theory and statistics to compute probabilities and to model continuous distributions such as the chi-squared and F distributions.


    The GAMMADIST function calculates the gamma distribution for a given set of parameters. The gamma distribution is a continuous probability distribution that is often used in statistics. It is commonly used to model the time between events. The function returns the probability density function or the cumulative distribution function for a given set of parameters.


    The GAMMA.DIST function calculates the gamma distribution probability for a specified x value, alpha and beta parameters. This function is often used in statistics to model continuous data that is skewed to the right. It can be used to analyze data in various fields such as finance, engineering, and social sciences.

Learn More

You can learn more about the GAMMAINV Google Sheets function on Google Support.